"Since Gabby arrived last Friday, we have noticed daily improvement in her neurological condition," Dong Kim, chief neurosurgeon at the hospital, said at a news conference in Houston. "In terms of recovering from brain injuries, this is lightning speed."

Giffords had been at the intensive care unit while doctors monitored the draining of cerebral spinal fluid that had built up in her brain, a common occurrence after severe head injuries. On Sunday, Kim said, the fluid was largely gone, and on Monday he removed the drain.

Although she already had started rehabilitation exercises in the intensive care unit, Giffords will continue to build up to a more rigorous schedule, said Gerard Francisco, TIRR's chief medical officer.

"We're working on conditioning, strengthening her range of motion," Francisco said.

She's also working with a speech therapist, although she is not yet able to talk. Giffords still has a tracheal tube in her throat, which is making it difficult to determine if she can speak, but doctors said that could be removed in the next few weeks.

Imoigele Aisiku, director of neurocritical care, said Giffords is "awake as much as you and I are. . . . She's cooperative and interactive and aware."